Tapered slot antennas, also known as Vivaldi antennas, have been developed for use in various applications. Usually, the width of the slot increases exponentially with distance from the feed point. In a typical implementation, the antenna is provided as orthogonal arrays of elements formed by conductive surfaces that define tapered slots therebetween. The conductive surfaces are usually formed on conventional printed circuit boards. More particularly, arrays of elements can be formed by using numerous printed circuit boards assembled in the form of a lattice array. Accordingly, such antenna arrays are sometimes referred to as “Vivaldi egg crate arrays”. These antennas typically provide a bandwidth of about 3:1 or 4:1, although some designs provide a bandwidth of about 10:1.
Although such designs can be effective, they can also be complex and difficult to manufacture. For example, in a typical Vivaldi array, multiple rows of elements can be provided by arranging multiple parallel rows of substrates having plated elements formed thereon. In order to provide a dual-polarized antenna, additional elements can be formed on multiple parallel columns of substrates having plated elements formed thereon that are arranged perpendicular to the rows of substrates. The rows and/or columns are slotted where they intersect, to form a plurality of cruciform conductive structures. However, such assemblies are prone to defects. For example, proper operation of the arrays requires a good electrical connection between orthogonal plated elements of the individual cruciform conductive structures, which is difficult to achieve. Moreover, the multiple boards are difficult to align and assemble.
In addition, the conventional balanced-to-unbalanced (BALUN) transition design for a Vivaldi antenna uses printed circuit board processes. Such BALUNs often include separate feed lines that extend across the tapered slot and that are terminated at a tapered element. BALUNs have also been proposed that incorporate radio frequency absorbing materials. However, most previous BALUN designs have been inefficient and difficult to manufacture.
Therefore, it would be desirable to provide a relatively reliable and robust phased array antenna. It would also be desirable to provide such an antenna that was efficient and that was relatively easy to manufacture.